One‐Pot Organocatalytic Michael Addition/I2‐Mediated Cyclization Sequence: Metal‐Free Synthesis of Spiropyrazolones from 1,3‐Diketones and Unsaturated Pyrazolones

A highly efficient organocatalytic Michael addition/I2‐mediated cyclization reaction sequence between 1,3‐diketones and unsaturated pyrazolones was achieved in the presence of a chiral cinchonidine‐derived squaramide catalyst and I2 under mild reaction conditions. A variety of optically active spiro...

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Veröffentlicht in:European journal of organic chemistry 2017-06, Vol.2017 (22), p.3152-3160
Hauptverfasser: Zhang, Xiao‐Long, Tang, Cheng‐Ke, Xia, Ai‐Bao, Feng, Kai‐Xiang, Du, Xiao‐Hua, Xu, Dan‐Qian
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Sprache:eng
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Zusammenfassung:A highly efficient organocatalytic Michael addition/I2‐mediated cyclization reaction sequence between 1,3‐diketones and unsaturated pyrazolones was achieved in the presence of a chiral cinchonidine‐derived squaramide catalyst and I2 under mild reaction conditions. A variety of optically active spiro‐dihydrofuran pyrazolones were obtained in good to high yields (71–97 %) with excellent diastereoselectivities and high to excellent enantioselectivities (up to >99:1 dr and 99 % ee). A gram‐scale synthesis of chiral spiro‐dihydrofuran pyrazolones was also successfully realized. A highly efficient organocatalytic Michael addition/I2‐mediated cyclization reaction sequence between 1,3‐diketones and unsaturated pyrazolones was achieved. A variety of optically active spiro‐dihydrofuran pyrazolones were obtained by using this method. The gram‐scale synthesis of chiral spiro‐dihydrofuran pyrazolones was also successfully realized.
ISSN:1434-193X
1099-0690
DOI:10.1002/ejoc.201700474